We have shown that several of the treatments known to maintain spermatogenesis in hypophysectomized rats (hCG, testosterone propionate (TP), pregnenolone) will maintain normal concentration of testosterone (T) in the rete testis fluid of hypophysectomized rats. To achieve a better understanding of the relationship between the levels of androgenic steroids in the tubular lumen and spermatogenesis, we propose to examine the concentration of T and DHT in the rete testis fluid and the morphology of the germinal epithelium in hypophysectomized rats under various experimental conditions. Specifically, we will measure the concentration of T and DHT in the rete testis fluid and blood of rats hypophysectomized before or after puberty and treated with TP starting two days or one month after hypophysectomy. We will also compare the effects of treatments with T or DHT on the concentration of these steroids in the rete testis fluid, as well as on the maintenance and restoration of spermatogenesis. Furthermore, we propose to examine the effects of FSH on androgen levels in the rete testis fluid, and on the initiation, maintenance or restoration of spermatogenesis in hypophysectomized rats treated with TP or pregnenolone. Finally, we are planning to examine the concentration of androgens in the rete testis fluid of vitamin A-deficient hypophysectomized rats treated with pregnenolone, and determine the concentration of steroids other than T and DHT in the rete testis fluid of intact rats at various ages under different experimental conditions. These experiments should provide new information on the hormonal control of spermatogenesis and on the distribution of steroids in the various compartments of the testis.